The object of the present invention is a method for delaying the run-off of flash-storm water or ordinary rainwater from roofs and other surfaces with a water-retention capability. The object of the invention is also a device for delaying the run-off of the flash-storm water or ordinary rainwater from roofs and other surfaces with a water-retention capability.
As a result of the intensive building activity in recent years, the sealing of the surfaces in development areas has increased. The flash-storm water falling on the sealed surfaces is thereby no longer slowly taken up naturally by nature but it runs off very rapidly together with a greater or a lesser amount of dirt. This has had the result that the government has taken steps in the case of larger buildings to retain flash-storm water on the spot upon, for instance, heavy rainfalls and/or to delay its further passage or seepage until later.
It has already been proposed, particularly in the case of flat roofs, first to collect the rainwater on the roof and then feed it in throttled fashion to the sewer. In order to compensate for large differences in temperature, a predetermined amount of water is frequently retained permanently on the roof.
In one known embodiment, the cross sections of the pipes leading from the roof to the sewer are correspondingly small so that only the prescribed permissible quantity can flow off.
In that case, to be sure, it is not sufficient merely to dimension the cross sections of the pipes suitably, but the laying of the pipes and their pitch as well as their hydraulic heights are all parameters which must be included in such a calculation. Accordingly, the design and the installation of such a run-off pipe system is very expensive and the positioning of the lines, especially if one proceeds in accordance with the principle of horizontally laid collector lines, frequently results in a high expense and in aesthetic problems within the building.